1. Field of the Invention
The present invention generally relates to a high performance resonant element. In particular, the present invention relates to methods and systems for processing a signal using a high performance resonant via.
2. Description of the Related Art
Signal lines and vias are both ubiquitous in circuit board and chip package technology. A signal line is capable of transmitting a broadband signal with high fidelity, while a via is necessary to connect signal lines that may reside on different levels within a laminated circuit board or to bring a signal from a signal line embedded between layers of a circuit board to the surface of the circuit board.
A via may be formed by drilling a hole completely through a circuit board and then plating the interior of the hole with a conductive material. In this manner, a via may form a hollow, conductive barrel-shape.
A via may be used to connect a signal line within a laminated stack of patterned layers within a circuit board to another signal line within the circuit board. FIG. 1 is a cross-sectional view of a circuit board 100 having plane layers 102, a pair of dielectric layers 104, and a signal line (signal trace) 106 between the pair of dielectric layers 104.
FIGS. 2A and 2b provide cross-sectional views of two other circuit boards 200 and 202 to illustrate two different types of vias and their relationships to signal lines that may be distributed across multiple levels within a circuit board.
FIG. 2A illustrates a through-type via 204. A through-type via 204 receives a signal from a signal line 206 at one level of the circuit board 200, carries that signal across substantially the entire length of the via 204, and provides the signal to another signal line 208 at another level in the circuit board 200.
Electrically a through-type via is the most benign type of via. In other words, a through-type of via generally has the least amount of detrimental effect upon a signal in comparison with other types of vias.
FIG. 2B illustrates a stub type of via 210. The stub via 210 receives a signal from a signal line 212 at one level in the circuit board 202 and provides that signal to another signal line 214 at substantially the same level within the circuit board 202.
One characteristic of a stub type of via is that there is a long section of via (hence the “stub” moniker), which is not necessary for propagating the signal. However, a stub via is generally unavoidable because of manufacturing cost constraints.
Stub vias are conventionally viewed as having very adverse effects upon signal propagation. Therefore, circuit designers conventionally further process these signals to address the adverse effects that these vias have upon the signal being transmitted. If it is not feasible to do so then, the signal impairments introduced by the stub vias may restrict the frequency content of the signal that can be transmitted. This often leads to a reduction in the signal bandwidth that the connection can support.
In particular, as illustrated in FIG. 2B, when a signal enters a stub via, the signal splits into two paths. One of those paths goes directly from the input signal line 212 to the output signal line 214. However, the other path entails a portion of the signal traversing the full length of the via 210, reflecting from the other end of the via, traversing back along the full length of the via, and then splitting a second time. One portion of that reflected signal returns to the input signal line 212 and the other portion of the reflected signal is carried onto the output signal line 214.
The portion of the reflected signal that is carried onto the output signal line 214 represents a delayed and attenuated replica of the original incident signal and will serve to contaminate subsequent signals traveling down line 214. Such effects may be particularly disadvantageous to a sinusoidal signal, and if the transit time, down and back from the end of the stub via is substantially equal to one-half of the period of the sinusoidal signal, then phase cancellation of the signal may completely attenuate the signal received from the input signal line 212.
Another type of via called is a “buried-type” of via (not shown) which does not extend to one of the outer layers of a circuit board. However, while it is possible to construct a buried-type of via, these types of vias require that holes be drilled in patterned layers before the layers are laminated together to form a circuit. This is a much more expensive process than drilling the holes after laminating the entire circuit board. Therefore, buried-type vias are not preferred.
Yet another type of via, called a “blind” via extends to one surface of the board and terminates on one of the internal layers of the circuit board. A blind via can be used to circumvent a via stub effect as well. However, a blind via also suffers from higher fabrication costs, and due to processing limitations, usually can only access layers close to one of the circuit board surfaces.